1. Field of the Invention
The present invention relates to a pinch-holder for a magnetic disc of the type in which a magnetic disc is pinched and is supported by disc pinching means.
2. Description of the Prior Art
A floppy disc unit is known and is used as an external memory for an electronic computer and the like. In this unit, a magnetic disc contained in a jacket is rotated and a magnetic disc or discs are brought into contact with the rotating magnetic disc for recording or for reproducing data on or from the magnetic disc.
As one type of such a floppy disc unit there is known a disc unit in which two magnetic heads are provided opposite to each other with one head being provided on the upper surface side of the magnetic head unit and the other head being provided on the lower surface side. FIG. 1 shows the essential part of such a known floppy disc unit.
In FIG. 1, the reference numeral 1 depicts a magnetic disc contained in a jacket 2. The jacket 2 is moved in the direction of arrow 3a until the magnetic disc 1 is positioned between two magnetic heads 10 and 11. Then, the magnetic disc 1 is turned about its center axis 4, that is the axis of rotation, by a driving means not shown. Next, a solenoid 5 is energized to rotate an actuator 6 about the rotation center, i.e. a fulcrum pin 7. The actuator 6 moves downwards in the direction of arrow 9a against the biasing force of a spring 8. Consequently, the magnetic disc 1 is pinched and is supported by the two magnetic heads 10 and 11 disposed opposite to each other which serve together as a pinch member. In this position, data recording or reproduction can be performed on the upper and lower surfaces of the magnetic disc 1 by the magnetic heads 10 and 11, respectively.
In the above known arrangement of disc unit, the gap formed between the two magnetic heads 10 and 11 is measured to allow the jacket 2 to be inserted into the gap. Taking into consideration the possible variation in thickness of the jacket, is required to be set at the gap size T a value larger than the jacket thickness t (T&gt;t). The thickness of the above mentioned magnetic disc is t.sub.1. Then, T&gt;t&gt;t.sub.1 and on the operation of the solenoid 5 the pinch member (magnetic heads) has be be moved over a relatively large stroke from T to t.sub.1 to pinch and to hold the magnetic disc. Since the stroke is relatively large, a strong impact force is applied to not only the magnetic disc 1 but also the magnetic heads 10 and 11 at the moment when the heads are brought into contact with the disc to hold the magnetic disc between the two magnetic heads.
Obviously, repetition of such an operation accompanied by a large impact will damage the magnetic disc 1 and deteriorate the characteristics of the magnetic heads 10 and 11. In the worst case, the magnetic heads may be broken. Moreover, large noise is generated for every solenoid operation.